Switch all user-facing time displays to 12-hour MM-DD-YYYY format

Consistently format dates and times across all templates and API
handlers using MM-DD-YYYY with 12-hour clock (03:04 PM):

- analytics.go: date keys, lastSync, lastRead timestamps
- progress.go: lastUpdated timestamp in GetAllProgress
- book_detail.templ: LastReadAt, DatePublished
- book_detail_modals.templ: progress sync timestamps, LastReadAt
- devices.templ: LastSync, LastSeen
- conflicts.templ: CreatedAt
- admin_users.templ: user CreatedAt date

templates/admin_users_templ.go

@@ -178,7 +178,7 @@ func AdminUsers(currentUser User, users []User, adminCount int) templ.Component
 				return templ_7745c5c3_Err
 			}
 			var templ_7745c5c3_Var8 string
-			templ_7745c5c3_Var8, templ_7745c5c3_Err = templ.JoinStringErrs(user.CreatedAt.Format("2006-01-02"))
+			templ_7745c5c3_Var8, templ_7745c5c3_Err = templ.JoinStringErrs(user.CreatedAt.Format("01-02-2006"))
 			if templ_7745c5c3_Err != nil {
 				return templ.Error{Err: templ_7745c5c3_Err, FileName: `templates/admin_users.templ`, Line: 89, Col: 106}
 			}